The present invention pertains to the electrical switch art and, more particularly, to an improved self contained proximity switch.
Numerous proximity switches have been developed in the prior art. Such switches are often positioned to sense the status of a moving object, such as a door. Thus, if the door is shut, a light is turned on or an indication is made that the door is secured.
In one type of prior art proximity switch, a plunger is depressed upon engaging the moving object. The plunger forces switch contacts to close causing associated circuitry to indicate proximity of the object.
In certain applications requiring proximity switches, the above mentioned force contact closing type switches are unsuitable. In one such application, proximity switches are positioned at the doorways of aircraft. Here, the switches are used to indicate to the flight deck the status of the various doors, i.e. that the doors are in position and locked. As it is crucial in aircraft applications that the switches work flawlessly over tens of thousands of operations, the above described forced contact switch proved unsuitable for reliability reasons.
Thus, a proximity sensor was developed which is capable of sensing the presence of a metallic object without the necessity of forcibly engaging the object. Such sensors could be placed in the proximity of doorways and, upon the door closing and coming within a predetermined distance of the sensor pickup, a signal is produced which is used by associated circuitry to indicate door proximity.
However, a failing in the above described proximity sensor is that for reliable operation it requires that a substantial area of some metallic object be brought within a specific tolerence of the pickup. In some applications, the object to be sensed does not present sufficient area for activating the sensor and/or the structural details of the mounting area provided for the sensor prevents proper alignment of the object therewith.
Thus, there has been a long felt need, particularly in the aircraft industry, for a highly reliable proximity switch which is adaptable to be configured in any of numerous different ways to allow mounting in the space provided.